Build a Rain Gauge and Weather Station With Your Kid

Weather prediction used to be wrong more often than not. A 5-day forecast in 1950 was barely more accurate than chance. Today, a 5-day forecast is roughly as accurate as a 1-day forecast was in 1980. The improvement comes from better numerical weather prediction models, more computing power, and — critically — more data. The global weather observation network now includes over 10,000 surface weather stations, 1,000+ radiosonde balloon launches per day, and millions of weather reports from ships, aircraft, and personal weather stations.

Personal weather stations contribute meaningfully to this network through Weather Underground and the Citizen Weather Observer Program. Your kid’s backyard instruments can join real meteorological databases. A rain gauge made from a plastic bottle and a ruler can upload data to the same network professional forecasters use.

Key Takeaways

• A functional rain gauge (plastic bottle + ruler) and wind speed estimator (Beaufort scale observation) cost nothing and produce real data
• Building an anemometer (cup-wheel wind speed meter) requires foam cups, a pencil, and a pin — under $2
• 30 days of weather data produces patterns: seasonal trends, storm correlation with pressure, rainfall totals
• Weather Underground and NOAA’s CoCoRaHS network allow kids to submit their measurements to real databases used by meteorologists
• Ages 8+ can run basic observation; ages 12+ can connect measurements to atmospheric science and map their data online

The Instruments: What to Build

Rain Gauge (Cost: $0)

A rain gauge measures how much precipitation falls during a rain event. The required instrument: any straight-sided container with a flat bottom.

Build: Find a straight-sided clear jar or plastic bottle (a 2-liter soda bottle with the top cut off, or a wide-mouth mason jar). Mark a ruler scale on the inside with a permanent marker or tape a paper ruler against the outside. Place outdoors in an open area, away from trees, walls, or anything that would block or redirect rain.

Read: After each rain event, read the water depth in millimeters or inches. Record: date, start time, end time, total depth. Empty the gauge after reading.

Important: The container must have straight vertical sides (not tapered). A tapered container gives inaccurate depth readings because the same volume of water occupies a different depth depending on the container width.

CoCoRaHS: The Community Collaborative Rain, Hail and Snow Network (CoCoRaHS), operated under NOAA’s National Weather Service, has over 20,000 volunteer observers across the U.S. who submit daily precipitation measurements online. Your kid’s data can be submitted here: cocorahs.org. The data is used by the National Weather Service, FEMA for flood modeling, and agricultural extension services. This is citizen science with immediate real-world application.

Anemometer (Cost: $1–3)

An anemometer measures wind speed by counting rotations of a cup wheel.

Build:

• 4 foam or paper cups (the cups catch wind)
• 2 straws
• A straight pin
• A pencil with an eraser
• A bead or small washer

Assembly: Cross two straws at their centers and tape them in an “X.” Tape a cup to each end of both straws (all cups facing the same rotational direction — all clockwise or all counterclockwise when viewed from above). Push a straight pin through the center crossing point and into the pencil eraser. The straw cross should spin freely around the pin.

Calibrate: On a calm day, take it in a car at a known speed (with another adult driving) and count rotations per second (mark one cup with a dot to track). At 20 mph, record your rotations per second. Now you have a rough calibration: [X] rotations/second = 20 mph. This is imprecise, but good enough for weather journaling.

Alternative: Use the Beaufort Scale (no instrument needed):

• Calm (0–1 mph): Smoke rises vertically
• Light air (1–5 mph): Smoke drifts slightly
• Light breeze (6–11 mph): Leaves rustle, wind felt on face
• Gentle breeze (12–19 mph): Small branches move
• Moderate breeze (20–28 mph): Dust raised, small branches sway
• Fresh breeze (29–38 mph): Small trees sway

Simple Barometer (Cost: $2–4)

Atmospheric pressure rises before clear weather and falls before storms. A barometer measures this.

Balloon barometer:

• Cut a balloon and stretch it tightly over the mouth of a glass jar, sealed with a rubber band
• Tape a long straw to the balloon surface, extending beyond the jar edge
• Make a scale on a card next to the straw tip

Reading: In high pressure (good weather coming), the balloon is pushed inward by the atmosphere, which tilts the straw up. In low pressure (storm coming), the balloon bulges slightly outward, tilting the straw down. Mark the straw position daily.

This device is sensitive to temperature changes as well as pressure — keep it in a consistent temperature environment for cleaner data.

The 30-Day Weather Log

The educational value of individual measurements is limited. The value of a month of data is substantial — it shows patterns, correlations, and seasonal trends. Set up a simple daily log:

Date	Precip (mm)	Wind (Beaufort)	Temp (°F)	Barometer reading	Sky condition
July 1	0	2	82	High	Clear
July 2	0	1	85	High	Clear
July 3	8.5	4	74	Low	Overcast → Rain

After 30 days: graph rainfall total by week. Compare your readings to the official NOAA weather station readings (available at weather.gov — find your nearest station). Calculate the correlation between barometer readings and next-day precipitation. This is data analysis with a real dataset — something very few science classes actually achieve.

How to Teach Your Kid About Meteorology and Data

Ages 8–10: The Observer’s Journal

The priority at this age is the habit of observation. Every morning, walk outside with your kid and record one sentence about the sky: “Partly cloudy from the northwest, wind light from the south, temperature around 75°F.” Use the Beaufort scale to estimate wind. After a week, ask: “What pattern do you notice?” Kids often independently discover that clouds before rain move differently (faster, different direction) than fair-weather clouds. That’s real meteorological observation.

Ages 11–12: The Correlation Investigation

After 30 days of data, ask your kid to create a scatter plot: barometer reading (x-axis) vs. rainfall in the next 24 hours (y-axis). Is there a correlation? In most temperate regions, falling barometric pressure reliably predicts precipitation. The strength of that correlation in your local data is a real data analysis question. Compare your correlation to published meteorological data for your region.

Ages 13+: Connect to Atmospheric Science

High pressure systems rotate clockwise in the Northern Hemisphere (and counterclockwise in the Southern); low pressure systems rotate counterclockwise. This is the Coriolis effect — Earth’s rotation deflects moving air masses. When your barometer reads low, which direction are the clouds coming from? Track over several storm events. Is the direction consistent with the Southern flank of a low pressure system? This connects ground observation to atmospheric dynamics at a scale of hundreds of miles.

The question to ask: “What information would we need to actually forecast the weather tomorrow — and what information does a professional meteorologist have that we don’t?”

Connecting to Professional Meteorology

The National Weather Service maintains about 900 Automated Surface Observing Systems (ASOS) stations across the U.S. that automatically measure temperature, dewpoint, wind, pressure, precipitation, and cloud ceiling every minute. The data feeds numerical weather prediction models (the GFS, NAM, and ECMWF models) that simulate the atmosphere as a 3D mathematical grid with grid cells typically 3–15 km on a side.

A 2020 analysis in Bulletin of the American Meteorological Society documented that personal weather station networks (like Weather Underground’s network of 250,000+ stations) provide valuable data in the gaps between official ASOS stations, particularly for localized weather events like microbursts, fog patches, and urban heat island effects (Bell et al., 2020).

Your kid’s rain gauge, registered with CoCoRaHS and uploading daily, is part of that network.

What to Watch For Over the Next 3 Months

Month 1 (data collection): Consistency is the challenge. Missing days are data gaps. Put the weather observation into a morning routine — same time each day is better than random-time measurements, which affects comparability. A week of data is not enough for patterns; push toward 30 days minimum.

Month 2 (analysis): The first time your kid notices a pattern independently — “it always rains a day after the barometer drops” or “wind from the northwest means the temperature drops within 12 hours” — is the payoff. These are real regional weather patterns, learned through data, not told through a textbook.

Month 3: Submit data to CoCoRaHS or Weather Underground. Looking at the online map with your measurement marked is a powerful motivator. Finding your station on a map alongside thousands of others — contributing to the same network professional forecasters use — makes citizen science feel concrete rather than abstract.

Frequently Asked Questions

How accurate is a homemade rain gauge?

A properly calibrated straight-sided container is quite accurate — errors of less than 10% are achievable. The main sources of error are: wind blowing rain sideways (the gauge is sheltered by trees), evaporation before reading (read within 30 minutes of rain ending), and tilted gauge (use a level). Professional tipping-bucket gauges at ASOS stations are accurate to ±0.01 inches — a homemade gauge is ±0.05–0.1 inches, which is adequate for educational and citizen science purposes.

What is CoCoRaHS and how do we join?

The Community Collaborative Rain, Hail and Snow Network (cocorahs.org) is a volunteer weather observer network operated with NOAA support. Joining is free. You register your gauge location on their map, then submit daily precipitation totals online or through their app. The data is publicly accessible and used by the National Weather Service. Observers receive a 4-inch diameter standard gauge ($10–15) or can use a homemade gauge.

Do we need to buy a thermometer?

Any thermometer works — even a dollar-store indoor/outdoor thermometer. For outdoor temperature measurement, place the thermometer in a shaded, ventilated spot (ideally a “Stevenson screen” — a white-painted louvered box — but even a shaded north-facing wall works). Direct sun on a thermometer reads 10–30°F above true air temperature, which skews your data.

How do we connect our data to what we see on the weather app?

Weather apps pull from the nearest official weather station, which may be miles away. Compare your gauge reading to the weather app’s precipitation for the same day. In many cases, local measurements differ significantly from the nearest official station — particularly in areas with complex terrain or isolated thunderstorms. This discrepancy is educational: weather is local, and the official network has gaps.

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About the author

Ricky Flores is the founder of HiWave Makers and an electrical engineer with 15+ years of experience building consumer technology at Apple, Samsung, and Texas Instruments. He writes about how kids learn to build, think, and create in a tech-saturated world. Read more at hiwavemakers.com.

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Sources

1. Bell, S., et al. (2020). “Assessment of the Influence of Weather Station Density on National Gridded Temperature Datasets.” Bulletin of the American Meteorological Society, 101(5), pp. E710–E724. https://doi.org/10.1175/BAMS-D-19-0228.1
2. CoCoRaHS. (2024). Community Collaborative Rain, Hail and Snow Network. https://www.cocorahs.org/
3. NOAA National Weather Service. (2024). Automated Surface Observing System (ASOS) Network. https://www.weather.gov/asos
4. Beaufort, F. (1806). Beaufort Wind Scale. UK Met Office. https://www.metoffice.gov.uk/weather/guides/coast-and-sea/beaufort-scale
5. Stull, R. B. (2015). Practical Meteorology: An Algebra-Based Survey of Atmospheric Science. University of British Columbia. (Open educational resource for meteorology.) https://www.eoas.ubc.ca/books/Practical_Meteorology/
6. National Science Foundation. (2022). Earth and Space Science: Weather and Climate Standards. https://www.nsf.gov/pubs/2022/nsf22060/nsf22060.pdf